Compensated winding



Janl 1957 w. T. HARRIS COMPENSATED WINDING 2 Smets-sheet 1 Filed Jan.22, 1954 FIG.V 2.

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Jan. 1, 1957 w. T. HARRIS COMPENSATEDWINDING 2 Shets-Sheet 2 Filed Jan.22. 1954 FIG. I6.

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ATTORNEYS nite 2,776,416 Patented Jan. l, i957 Erz! coENsArun Wilsons@Application January 22, 1954, Serial No. 465,614

20 Claims. (Cl. 340-11) My invention relates to an improved core andwinding construction for electro-magnetic circuit elements and is of`application to electro-acoustic transducers, to electromagneticinductors, to transformers, and the like. rhis application is acontinuation-in-part of my copending application Serial No. 318,720,filed November 4, 1952.

It is an object of the invention to provide improved devices of thecharacter indicated.

It is a specific object to provide an improved core and windingconstruction having the basic virtues of toroidally wound cores withoutrequiring the elaborate fabrication techniques necessary with toroidalwindings.

It is another specific object to provide an improved construction of thecharacter indicated in which stray hum and other pickup `may becompletely and inherently compensated for and, therefore, effectivelyneutralized.

Other objects and various further features of novelty and invention willbe pointed out, or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

Fig. l is a longitudinal sectional View through an electro-acoustictransducer incorporating features of the invention;

Fig. 2 is a sectional view in the plane 2-2 of Fig. `1;

Figs. 3 and 4 are simplified fragmentary views partially in section andillustrating alternate ernployments of my transducer in electro-acousticarrays;

Figs. 5 to 8 are simplified longitudinal sectional views of alternatecircuit elements incorporating features of the invention.

Figs. 9 to 16 are views corresponding respectively to Figs. 1 to 8 butillustrating another basic winding arrangement.

Briefly stated, my invention contemplates anew core and windingconstruction employing what may be termed 'a toroidal core, therebyproviding a generally toroidal flux path; a first, or signal winding, iscoupled to the core path and to the stray-flux path, and a second, orcompensating winding, is coupled to the stray-linx path to the exclusionof or effectively independently of the core path. The first and secondwindings may have substantially the same number of turns and may beconnected in opposition, so that any coupling to the stray-tlux pathwillV be completely neutralized, and coupling to the core will, ineffect, be exclusively promoted. In the general form represented byFigs. 1 to 8, the second or compensating winding is physically locatedradially inside the toroidal flux path and, therefore, radially insidethe first or signal winding; in the general form represented by Figs. 9to 16, the second or compensating winding is physically located radiallyoutside the torodal ilux path and, therefore, radially outside the firstor signal winding.

In application to electro-acoustic transducers, the core may be ofmagnetostrictive material, at least in those parts of the core in whichmagnetostrictive elongations are desired. Thus, `in-one subgeneric formof the invention, the toroidal core may comprise two generallyconcentric elongated cylindrical magnetostrictive members with magneticmeans radially closing and interconnecting the ends of said cylinders todefine. the toroidal ilux path. In application to circuit elements, thesame general core construction may be employed, or the cylindricalmemcylindrical members are assembled to each other.

bers may be integrally formed with end-flange means, in order to permitcompletion of the toroidal path when the By way of illustratingcircuit-element applications, I shall also describe transformer andinductor constructions.

Referring to Figs. l and 2 of the drawings, my invention is shown inapplication to an electro-acoustic transducer` specifically designed forunderwater use. As indicated generally above, the construction featuresa core providing a generally toroidal flux path; in the form shown, saidcore happens to be built up from aplurality of elements designed topromote principal acoustic response generally along the axis of thetoroid, The core elements may thus comprise inner and outer tubularmembers litilll of magnetostrictive material, as, for examplesheet-metal alloy of a composition known to the trade as Permendur. Thesheets may be relatively thin and overlapped at their longitudinallyextending edges, as at 12-ll3, after applying a thin layer of insulationbetween the overlapping areas in order to reduce circulating eddycurrents. The toroidal path may be completed by means of end closurecaps ltd-i5 of magnetic material in magnetic-flux-conducting relationwith both cylinders itl-11. For simplicity of fabrication, I have shownthe end members 14-15 to be circular discs of magnetic ceramic material,such as a ferrite.

directed from left-to-right axially along the inner cylinder 10, thenradially outward in end cap 14, then right-tcleft axially along theouter cylinder 11, and finally radially inward in end cap 1S. The secondor compensating winding 17 is wholly linked to the stray-flux path tothe exclusion of the core path and may, therefore, be contained withinthe inner tubular member 10. In order to achieve full compensation forstray flux, the number of turns on the two windings 1.6-1.7 ispreferably the same, and these windings are connected in opposition, assuggested by the portion 18 of the conductor material interconnectingthe right end of the two windings through a small opening in the tubularmember lo.

The entire transducer may be contained within a housing 19, which may bea metal casting, and pressurerelease means 20, such as a layer of corkor air-filled rubber, may line the excavated interior of the housing 19and, therefore, peripherally envelop the toroidal core. Diaphragm means21 may llexibly seal 4off the housing opening, and leads to the twowindings may be carried out the closed end of the housing, as to a leadcable 22 passing through a suitable end fitting 23.

It will be seen that the described construction lends itself torelatively simple fabrication with common coilwinding machines andtechniques; for example, the inner winding 17 may be applied as acontinuous helix on. a cylindrical form, such as a cardboard roll or aplastic rod or tube, as shown at 2d. In a separate and equally simpleoperation, the outer winding 1.6 may be applied as a single continuoushelix over the periphery of the inner tubular member 10; of course, topreserve insulation, the wire itself may be insulated as, for example,

enamel-coated, or the cylinder may be coated with so as to ll air spacesat 27-23; the potting compound at 272S is preferably of thesound-transmitting characteristics of the medium (e. g. water) in whichthe transducer is to be employed, and with vacuum-immer? sion thepotting material may be brought into intimate pressure-transmittingrelation with all exposed active internal surfaces of the transducer (i.e. surfaces of cylinders 10-11 and of end plates 14-15). The basictransducer unit may then be inserted in the housing I9, which maypreviously have been lined with the pressure-release material 20, andthe assembly may be made completely rugged by further potting in thespace 29. Finally, in order to sealol all possible crevices, a boot orcoating 30 of plastic, rubber, or rubber-like material may be appliedlo-ver the entire assembly, as in a dipping process.

In Figs. 3 and 4, I show alternate employments of my basic transducerconstruction, as in multiple-element arrays. In Fig. 3, the arraycomprises within a housing a plurality of independent core units orVtransducer elements 36-37-3S-39, each of which may be of essentially thesame construction as that part of the structure of Figs. l and 2 as isfully contained within the toroidal core l0l1-ll415- It will beunderstood that lead connections and winding interconnections have beenomitted in Fig. 3 for the sake of clarity, but that for each transducerelement the leads may be brought out of the rear end in the mannerdescribed in Fig. l, and interconnected to each other by known methodsto achieve directional or other array functions. The array is completedin Fig. 3 by having all active faces 14 of the cores of transducerelements 36-37-38-39 aligned in'essentially the same thrusting surfaceand intimately related to a common diaphragm 40, which may be periph-Verally bolted, las suggested at 41, to the housing 35.k

Lateral pressure-release means such as cork liners may effectivelyenvelop the transducer units of Fig. 3 but for certain applications thedesired lateral release may be achieved by merely not lling the spacesbetween these elements and, therefore, by leaving them exposed to airWithin the remaining volume in the housing 35.

In Fig. 4, the array is contained within a housing 45 which may be thesame as that described in Fig. 3 and,- again, common diaphragm means areapplied over all transducer elements. However, in Fig. 4 the transducerelements are never completed until fully assembled into the array. Thisis because end closures for the toroidal core paths are formed at oneend by a single plate 46 of magnetic material, as of magnetostrictiveceramic, and at the other end by a similar plate 47.

In assembling the array of Fig. 4, therefore, the inner and outercylinders ltr- 11 may be assembled and wound and potted in the manneralready described, except that end-closure plates are omitted in thispreliminary assembly. Toroidal llux paths are completed only when theend plates 46-47 are applied in place. 46-47 may be retained bytie-bolts (not shown) extending therebetween, but sufficient adhesion ofthe assembly may result if thewound core elements 1li-lll are pottedwith a slight excess of potting material, so that upon localized heatingof the plates 46-47, when squeezed to the wound tubular members liti-1I,the plastic itself will be permitted to permeate the micro- Vscopicinterstices of the plates #t6-47, so as to provide a sufficiently rigidbond upon setting of the plastic. Thus, in Fig. 4 the basic array isseen to be completed again by employment of common diaphragm means, andthe diaphragm means in Fig. 4 may be viewed as constitut- The end platesing either the forward thrust plate 47, or the combination of the plate47 with the flexible diaphragm 48.

In Fig. 5, I show an application of the principles of my invention to acircuit element which may be a transformer. The circuit element is seento comprise a toroidal core path defined by inner and outer tubularmembers 5tlg-51, between end-closure pieces SZ-SS. A first signalwinding 54 is linked to the core path and to the stray-linx path, and afirst compensating winding 55 is linked only to the stray-flux path andis connected in opposition to the signal winding 54. The describedwindings 54-55 represent a complete parallel with the construction ofFig. l and may constitute the primary of the transformer. Thetransformer secondary may include a signal winding 56 linked to the samecore path and also to the stray-llux path, and a compensating winding 57linked only to the stray-flux path. The secondary windings 56-57 mayalso be connected in opposition, and primary and secondary leads may bebrought out through appropriate access holes at opposite ends of thedevice, as at 58-59, respectively. For complete compensation andassurance against stray pickup, I prefer that the signaland compensatingwindings 54--55 for the primary shall have the same number of turns, andthat the secondary (signal and compensating) windings 56-57 shall alsohave the same number of turns, as will be understood. Y

In Fig. 6, I illustrate a slight variation of the basic constructionwherein the toroidal core path is defined entirely by magnetic ceramicmaterial. Thus, inner and outer tubular members 60--61 may be ceramiccylinders, and the toroidal path may be completed by ceramic end plates162-63. The signal and compensating windings 64-65 may be coupled to thecore path and to the strayflux path, as described above. The device ofFig. 6 will be seen to represent a good electro-acoustic transducerconfiguration, or merely a circuit-element inductance; and, of course,the inherent freedom of magnetic ceramics from eddy-current problemsavoids the necessity of resorting to insulated overlapping ends (as at12-13 in the construction of Figs. 1 and 2). Thus, the cylinders 64I-61may be circumferentially continuous.

In Fig. 7, I illustrate a simplified transducer or circuitelementconstruction, wherein the toroidal core path is defined by two partswhich may be said to include inner and outer cylindrical members 67-68with cooperating end flanges 69-70 to complete the toroidal path. Thus,the inner tubular member 67 may be integrally formed at one end with aradial outwardly extending flange 69, and the outer tubular member 68may be integrally formed at the other end with a radial inwardlyextending ange 70. It will be noted that the ange 70 extends all the wayradially inwardly so as to make the part 68-70 constitute a cup with aclosed bottom. Assembly may be made by applying the signal Winding 71 tothe outer surface of the inner tubular member 67 and by bringing onelead thereto through a small access opening v72 at the base of ange 69.The inner, or compensating winding 74, may be applied to a projection 75integral with a plastic closure 76 for one end of the device.l Leads73-77 may both be brought out through the base of the plastic closure76; and, if desired, a further plastic layer 78 may be applied, as bydipping, to encase the entire device or to complete its enclosure, assuggested at 78.

In Fig. 8, I illustrate another transformer embodiment, which maygenerally resemble the construction of Fig. 5. Thus, in Fig. 8, atoroidal magnetic core path may be established by cylinders 80-81,capped by end plates 82-83. A signal winding 84 may be linked to thecore path and to the stray flux, and a compensating winding 85 may belinked to the stray flux to the exclusion of the core Vpath. Theelectrical input and output connections 86-87, respectively, illustratean autotransformer use of the described parts. Thus, input leads 86 maybe connected across a small number of the turns of signal Wind- 4, andoutput leads 87 may be connected across the signal winding 84. Thecompensating winding 85 heed not be connected as an autotransformer, andI have illustrated connection of winding 85 merely in series with oneoutput pole of the signal winding 84. With the compensating winding 85thus connected in opposition to the signal winding output, fullneutralization of stray-flux pickup may be achieved without the need toconnect the compensating winding as an autotransformer.

In Figs. 9 to 16, I illustrate the other general form of the invention,as appliedlto structures analogous to those described in detail inconnection with Figs. 1 to 8. According to this other general form ofthe invention, coupling of the second winding to the stray flux (to theexclusion of the toroidal core path) is accomplished eX- ternally of, orradially outside, the core structure.

Thus, in Fig. 9, the transducermay comprise a generally toroidal fluirpath established by axially overlapping and substantially coextensivecylindrical members 90-91 of magnetostrictive material, joined at theirends by magnetic material, such as discs 92-93 of magneticoxide ceramic.The rst or signal winding 94 may be developed on the inner cylindricalmember 90 and may thus be coupled to the toroidal fluxpath and to anystray-flux path to which the transducer may be exposed. The sec ond orcompensating winding 95 may be developed, preferably with the samenumber of turnsas winding 94 and axially substantially co-extensivetherewith, over the outer cylindrical member 91. By connecting windings94-95 differentially, as suggested at 96, the leads 97 may respondsubstantially only to the ux circulated in the toroidal path.Pressure-release means, housing means, a diaphragm, and other elementsof the structure of Fig. 9 may be as described for Fig. 1 and havetherefore been given the same reference characters.

The transducer arrays of Figs. 11 and 12 generally resemble those ofFigs. 3 and 4, except that to illustrate the other general form of ftheinvention the second or compensating winding 100 has been developedradially outside the outer cylindrical member- 101, and the rst orsignal winding 102, although radially inside the compensating winding100, is still coupled to thetoroidal ux path by way of the innercylindrical member 103. In Fig. l1, the individual transducer elementsare formed with complete magnetic circuits, completed in each instanceby separate magnetic end discs 104--105; whereas, in Fig. 12, magneticend plates 106-107 complete the toroidal ux paths of a plurality oftransducer elements in common.

In Fig. 13, I illustrate the plane transformer case in which a primarysignal winding 110is developed about the inner cylindrical core member111, and in which the primary compensating winding 112 is developedabout the outer cylindrical core member 113. Corresponding signal andcompensating secondary windings 114 and 115 are developed about the samecylindrical members 111-113 and, except for the relative radial relationof the various windings, the construction and functioning 'of thetransformer of Fig. 13 resembles that of Fig. 5.

In Figs. 14 and 15, the reversed placement of the compensating windingwith respect to the signal winding has been effected in a mannercompletely analogous to that described in Fig. 13, and therefore theparts in Figs. 14 and l5 which correspond respectively to those in Figs.6 and 8 have been given the same reference characters, with primednotation.

The circuit element of Fig. 16 is generally similar to that of Fig. 7,except again that the second or compensating winding 74 has beendeveloped outside the outer limits of the core member68. The rst orsignal winding 71' is linked to the toroidal flux path established byiianged cylindrical members 6970, and the full assembly is sealed as aunit by a plastic potting, suggested at 76'-78.

It will be seen that I have described a basically simplewinding-and-core construction lending itself to massproductiontechniques which are already well understood and for which there is arelative abundance Yof machinery. My construction avoids the undesirableproperties (i. e. susceptibility to stray liux) characteristic ofhelically-wound constructions madewith such existing techniques andmachinery. While it has been possible in the past to avoid theseundesirable characteristics by Y resorting to complex fabricationmethods and expensive machinery, my construction ,avoids the need forsuch complexity and expense.

While I have described the invention in detail for thev preferred formsshown, it will be understood that modifications may be made within thescope of the invention as dened in the claims which follow.

I claim:

l. In a device of the character indicated, a toroidal core path deningan annular space within said core path, a rst winding contained withinsaid annular space and coupled to said core path and to the stray flux,and a second winding differentially connected to said rst winding andwound radially outside the body of said core and therefore coupled tothe strayflux to the exclusion of said core path.

2. In a device of the character indicated, core-body means containingand defining a continuous toroidal magnetic-flux path, a rst windinglinked to said path, whereby said iirst winding is also linked to thestray/flux path in which said core means may be immersed, and a secondwinding differentially connected to said first winding, the axis of saidsecond winding'being substantially coaxial with that of said rst windingand said second winding being linked to said stray-flux path to theexclusion of said core path.

3. A device according to claim 2, in which the number of turns of eachof said windings is substantially the same.

4; A device according to claim 2, in which said core means includes amagnetic ceramic.

5. A device according to claim 2, in which parts of said core meansextending axially of said toroidal path are of magnetostrictivematerial.

6. In a device of the character indicated, two substantially concentricelongated cylinders of magnetic material, a rst winding enveloping theinner of said cylinders and within the outer of said cylinders, a secondwinding wholly enveloping the outer of said cylinders, and closure meansof magnetic material radially interconnecting the ends of said inner andouter cylinders, whereby a toroidal core path is defined with said firstwinding linked to said core path and to the stray-ux path in which saiddevice may be immersed and with said second winding linked to saidstray-flux path to the exclusion of said core path.

7. In a device of the-character indicated, two elongatedmagnetostrictive generally cylindrical members one within the other andmagnetically interconnected at their corresponding ends, whereby agenerally toroidal ux path is thereby defined, a first winding in theradial space between said members and therefore coupled to said fluxpath, and a second winding radially outside the outer of said membersand therefore not coupled to said flux path, whereby upon differentialconnection of said 4 windings stray-field effects comrncn to bothwindings may be substantially eliminated.

8. A device according to claim 7, in which said generally cylindricalmembers are axially substantially coextensive, and in which theinterconnection of said members is effected by end closure members ofmagnetic ma- .10.- A device accordingto claim 9, in which said angemeans comprises an outwardly extendinglradial flange at one end of theinner member, andan inwardly extending. -radial ange at-theother end ofthe Youter member. l1. A device according to claim 7, in which saidmembers are of magnetostrictive ceramic material.

12. An electro-acoustic transducer, comprising a magnetic core-bodyincluding.magnetostrictive means at least in axially extending partsthereof, said core-body defining a generally toroidal iiux path, a rstwinding linked to said ux path and to a stray-flux path, and a secondwinding differentially connected to said first winding, said secondwinding being unenclosed within the torus of said core-body andtherefore linked to said stray-linx path to the exclusion of flux insaid core-body, and pressure-release means circumferentially envelopingthe periphery of said core-body. i

13. In a transducer of' the character indicated, a relatively rigidhousing having an excavated interior opening to one end thereof, amagnetic core-body establishing sure-release means radially isolatingsaid core-body fromA said housing, and a diaphragm in intimate axiallydirectedl pressure-transmitting'relation with that end of said core'-body whichy faces out of said opening.

14. In a multiple-element transducer of the character indicated, aplurality of cores of magnetostrictfive material establishing for eachcore a generally toroidal flux path, said cores being aligned with theirthrust faces sub.- stantially in a common surface, there being for eachcore a first windng enclosed within the torus of the core `and linked tothe core path and to a stray-flux path, and a second windingdifferentially connected to said irst winding and unenclosed within thetorus of the core and therefore linked solely to the stray-flux path,and diaphragm means common to the thrust faces of all said elements. 15.A' transducer according to claim 13, in which said cores are completelyself-contained separate and inde- 'sf pendent elements, and in whichsaid diaphragm met.,v separately connected to each of said units.

16. A transducer according to claim 13, in which the thrust end of eachof said cores is closed by a single piece of magnetic material common toall -thrust ends of said cores and separately closing the toroidal lluxpaths in all of said units, whereby, said single common piece ofmagnetic material may constitute said diaphragm means.

17. A transducer according to claim 15, in which a second similar pieceof magnetic material closes the other ends of all said core units incommon.

18. ln a multiple-element transducer of the character indicated, aplurality of cores of magnetos'trictive material establishing for eachcore a generally toroidal flux path, said cores being aligned with theirthrust faces substantially in ,a common surface, there being for eachcore a first winding linked to the core path and to a strayux path, anda second winding differentially connected to said lirst winding andlocated radially outside said toroidal ux path `and linked solely to thestray-flux path, and diaphragm means common to the thrust faces of allsaid elements. i

19. In a device of the character indicated, a core comprising twoelongated magnetic ceramic cylindrical menibers, one within -the other,`magnetic ceramic elements interconnecting said ceramic Vmembers attheir'corresponding ends, a first Winding in the radial space betweensaid members and therefore coupled to said core, and a second windingsubstantially coextensive with said irst ywinding but independentofeffective coupling to said core,A

whereby upon` differential connection of said windings stray-fieldeffects common to both windings may be substantially'eliminated. y

20. In a device of the character indicated, a core comprising twoelongated cylindrical members of magnetic material one within the otherand magnetically interconnected at their corresponding ends, a firstwinding in the radial space between said members and therefore coupledto said core, and a second winding substantially axially coextensivewith said first winding but independent of effective coupling to saidcore, whereby upon differential connection of said windings stray-fieldeffects common to both windings may be substantially eliminated.

No references cited.

